The present invention generally relates to a keyboard, such as a computer keyboard, and in particular to a pushbutton structure of a keyboard which generates a pulse-like reaction when it is depressed for indicating the depression thereof.
A computer keyboard includes a plurality of pushbuttons each comprising a cap accessible and depressible by a user. A conventional design of the pushbutton comprises a post, which may be hollow, extending from the cap. The post is partially received and is axially movable within a guiding bore. To ensure proper movement of the cap, the post must have a size large enough to reduce the risk of being jammed in the guiding bore. This, however, is contrary to the current trend of miniaturization in the electronic and computer industries.
Pushbuttons having caps supported by a pair of links pivotally connected to each other in a cross form are also known. This structure effectively reduces the space required by a pushbutton. A rubber member is positioned under the cap. The depression of the cap collapses the rubber member. The resiliency of the rubber member restores the cap back to its original un-depressed position. Such a restoration force provided by the rubber member, however, is generally not sufficient to effectively return the cap back to the un-depressed position.
Furthermore, the rubber member only offers a very limited reaction during the depression of the pushbutton. This may sometimes be ignored by the user when the user is depressing the pushbutton and thus making no clear indication of the depression of the pushbutton to the user.
It is thus desirable to provide a pushbutton structure which overcomes the above problems.
Accordingly, an object of the present invention is to provide a pushbutton structure which generates a pulse-like reaction during depression of the pushbutton for providing a clear indication of the depression of the pushbutton.
Another object of the present invention is to provide a pushbutton structure having a strong restoring force for returning the pushbutton from a depressed position to a released position.
To achieve the above objects, in accordance with the present invention, there is provided a pushbutton structure of a keyboard comprising a cap supported on a base board by a linkage comprising first and second links pivoted together whereby the cap is movable from a released to a depressed positions when depressed. Each link has upper and lower pivots respectively connected to the cap and the base board. The links have two side bars connected between the upper and lower pivots thereof Two spring arms extend from the base board having free ends forming L-shaped offset sections receivingly engaging L-shaped recesses defined in corresponding side bars for biasing the cap toward the released position. The spring arms deform when the cap is depressed. When the spring arms are deformed to an extent, the offset sections are abruptly driven toward and impact a contact surface of the recesses, generating a sound of impact and a pulse-like reaction caused by the impact. The deformation of the spring arms helps returning the cap back to the released position when the depression is released.